DESCRIPTION: Allegheny University of the Health Sciences/MCP Division (AUHS/MCP) and the Riverside Research Institute (RRI) will collaborate in the investigation of ultrasonic tissue characterization (UTC) of carotid atherosclerotic plaque. The goals are to develop UTC methods to identify the constituents of carotid plaque that are likely to indicate risk of cerebral embolism, and to evaluate how well the application of the developed methodology correlates with present and future symptoms of transient ischemic attacks and strokes. The research is designed to identify the UTC features that best correlate with the histology of carotid endarterectomy specimens, determine the scattering basis of observed UTC parameter values for plaque constituents, determine the UTC features that best correlate with existing neurologic findings, assess perspectively the value of UTC as a diagnostic test to predict neurologic events. A UTC methodology developed by RRI employing quantitative spectrum analysis of backscattered echoes will be further tailored and refined for carotid plaque applications. Scattering theory development directed to enhancing UTC of carotid plaque will employ acoustic microscopy to establish UTC in a more basic, physical context to improve the ability of UTC to more precisely characterize carotid plaque constituents.